Tunable spoof surface plasmon polariton transmission line based on ferroelectric thick film

Spoof surface plasmon polaritons (SSPPs) provide a high field confinement in the sub-wavelength scale and low transmission loss in the propagation, which are widely used in microwave functional devices. In this paper, we first propose a tunable SSPP transmission line (TL) based on ferroelectric thick film. The ferroelectric thick film associated with the SSPP planar waveguide can provide an electrically tunable transmission phase. Two electric-field-coupled inductive–capacitive (ELC) resonators are added in the configuration to inspire the coupling between ELC resonant modes and SSPPs, enabling the tunable TL to work in the frequency-selective transmission passband. It is demonstrated that the SSPP mode can be designed in higher or lower confinement to modulate the electromagnetic field strength inside the ferroelectric thick film. This property promotes a balanced design between low transmission loss and large phase change for tunable TL. As a result, this study provides an alternative route to design tunable SSPP devices based on ferroelectric thick film, which may open up new applications in tunable microwave devices.